1. Field of the Invention
The present invention relates to an image processing mechanism, and more particularly, to an image processing method and a related apparatus for interpolating a target image block thereby effectively preventing artifact phenomenon.
2. Description of the Prior Art
In an image interpolation process, a motion vector is determined and utilized to interpolate an image block to the position to be interpolated in order to generate an image block that is required by a position to be interpolated in an interpolated frame between two frames. In some special cases, however, the artifact phenomenon will be visible to the human eye if the motion vector is directly utilized to interpolate corresponded image blocks to the position to be interpolated. Please refer to FIG. 1. FIG. 1 is a diagram of a conventional image processing mechanism for generating an image block required by a position to be interpolated. The frames Fn-1 and Fn are consecutive frames, and the conventional mechanism performs an image interpolation to the frames Fn-1 and Fn so as to generate an interpolated frame F′ (as shown by the dotted line in the figure). For simplicity of illustration, FIG. 1 only shows illustrative patterns of different image blocks on a certain horizontal position of the frames Fn-1 and Fn. In practice, the image blocks A1 and A1′ of the frames Fn-1 and Fn correspond to the same image object moving horizontally, and other image blocks such as A2 and A2′ represent the same background of the horizontal position in the frames Fn-1 and Fn. As shown in FIG. 1, the image object corresponding to the image block A1 moves to the position P1 in the interpolated frame F′. According to the motion estimation result of the conventional image processing mechanism, the image object corresponding to the image block A1 is estimated to move to the position P1 in the interpolated frame F′ by referring to the image blocks A1 and A1′ of the frames Fn-1 and Fn, so the image block A1″ can be interpolated precisely at the position P1. Similarly, it can also be determined that the image object corresponding to the image blocks A2 and A2′ is supposed to be at the position P2 in the interpolated frame F′ by referring to the positions of the image blocks A2 and A2′ (that is, the background part) in the frames Fn-1 and Fn, so the image block A2″ can therefore be correctly interpolated at the position P2.
However, when the conventional image processing mechanism is about to interpolate the image at the position P3 in the interpolated frame F′, an artifact phenomenon which may cause a serious image distortion will be possibly generated because an image object corresponding to the image block A1 has moved to the position P1 in the interpolated frame F′ and therefore the position P3 is supposed to show the background part originally covered by the image object. However, when the conventional image processing mechanism calculates the minimum pixel differences to perform motion estimation, an image block which is similar to the image block at the position P3 in the frame Fn-1 cannot be found at the same position P3 in the frame Fn. This is because the background part at the position P3 was covered by the image object corresponding to the image block A1. Even though a motion vector corresponding to a certain minimum sum of absolute difference (SAD) of pixel values can still be found, utilizing the motion vector to generate the image block at the position P3 in the interpolated frame F′ may cause more serious image distortion or the artifact phenomenon; for example, the unwanted image block A″ may be generated at the position P3 in the interpolated frame F′.